Field of the Invention
This invention relates to a means for applying liquid in the form of a spray to a surface afforded by a relatively moving member (herein called the treated member) and over which such liquid is required to be distributed. Such means are referred to herein as being of the kind specified.
The invention has been developed primarily to meet the requirements which arise in lithographic offset rotary printing presses. In such presses the lithographic printing plate is mounted on a rotary cylinder (herein called the plate cylinder) and has non-printing areas which will accept, and are required to be moistened by, water or other ink repellent liquid, and printing areas which are required to be moistened by ink. The non-printing areas are moistened first and the aforesaid ink repellent liquid and the ink is of such composition (normally oil based) that it will then be accepted only on the printing areas.
It is important that the quantity of the aforesaid liquid delivered to the printing plate shall be controlled so that it is sufficient to wet the non-printing areas and hence be effective to prevent ink pick-up on these areas, but not so great that a surplus tends to run onto the printing areas and thereby prevent these being properly inked. The ratio of printing area to non-printing area varies appreciably in different classes of work and it is, therefore, necessary to be able to vary the supply of water or ink repellent liquid in conformity with such variations. Also there are other parameters of a variable character which require the quantity of said liquid to be varied from time to time.